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Question 8

Remembering that the surface temperature of the Sun is ~6000K, a red giant would have a temperature of:
Answer Selected Answer:

30,000 K
Correct Answer:

3000 K
Response Feedback:

Incorrect, a red giant like Arcturus is ~1/2 the (surface) temperature of the Sun. A 30,000 K star is an O star like Rigel and the Earth is ~300 K.

Question 6
0 out of 3 points You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster? Answer Selected Answer: 4.6 billion years. Correct Answer: 10 billion years. Response Feedback:

Incorrect, stars like the Sun live 10 billion years
0 out of 3 points

Question 5

Why does the fusion of hydrogen release energy to power the Sun and stars?
Answer Selected Answer: Correct Answer: c.

fusion breaks up hydrogen molecules, releasing energy.
b.

fusion combines 4 hydrogen atoms into one helium which has less mass than 4 protons Incorrect, this mass difference powers the stars, think Einstein's equation E = m c2, the energy released is proportional to the mass difference. If helium was more massive than the 4 hydrogen atoms the stars would not shine.

Response Feedback:

Question 3
0 out of 3 points

We currently know of approximately how many exo-planets?
Answer Selected Answer:

9000
Correct Answer:

900
Response Feedback:

Incorrect, see the exo-planets encyclopedia for the latest numbers

A constellation is
Answer Selected Answer: d.

members of a single star cluster
Correct Answer: c.

stars at varying distances in the same part of the sky
Response Feedback:

Incorrect, the stars in a constellation are not necessarily members of a single star cluster. stars in a single cluster are approximately the same age and distance. Constellations are just pretty pictures in the sky created by our ancestors to tell stories.

Question 14
0 out of 3 points When we see a region of a planet that is not as heavily cratered as other regions, we conclude that Answer Selected Answer:

the planet formed after the age of bombardment and missed out on getting hit by leftover planetesimals.

Correct Answer: Response Feedback:

the surface in the region is younger than the surface in more heavily cratered regions.

Incorrect, the regions that have been reformed via vulcanism, erosion, etc most recently have fewer craters
0 out of 3 points

Question 15

Incandescent light bulbs have a temperature of ~2700 K, this means that their light is emitted mostly:
Answer Selected Answer:

at optical wavelengths
Correct Answer:

at infrared wavelengths
Response Feedback:

Incorrect, the cooler temperature (relative to the Sun) means that these bulbs emit most of their light at longer - infrared - wavelengths. This is why they are so inefficient.

Question 17

0 out of 3 points What happens to the core of a star after it ejects a planetary nebula? Answer Selected Answer: It becomes a neutron star. Correct Answer: It becomes a white dwarf. Response Feedback:

Incorrect, this is the path stars like the Sun take in becoming white dwarfs
0 out of 3 points

Incorrect, open clusters typically contain fewer stars (1,000) than the globular clusters (~100,000-1,000,000) which formed early in the galaxies history.
0 out of 3 points

Question 22

The Sun will most likely never become a nova or type Ia supernova because such events only happen to stars that
Answer Selected Answer:

are much more massive than the Sun
Correct Answer:

are in close binary systems
Response Feedback:

Incorrect, novae and type Ia supernovae occur in binary systems where one member is a white dwarf. Remember that high mass stars become type II supernovae.

Question 23
0 out of 3 points On a Hertzsprung-Russell diagram, where on the main sequence would you find stars that have the greatest mass? Answer Selected Answer: lower right Correct Answer:

upper left Response Feedback:

Incorrect, O stars have the largest mass
0 out of 3 points

Question 27
How thick are Saturn's rings from top to bottom? Answer Selected Answer: a few kilometers Correct Answer: a few million kilometers Response Feedback:

Incorrect, the rings are incredibly thin

An M-star which is 1/1000th the luminosity of the Sun an 1/10th its mass should live approximately
Answer Selected Answer: b.

1 billion years
Correct Answer: d.

1 trillion years
Response Feedback:

Incorrect, since the amount of energy it puts out is 1/1000th that of the Sun but it has only 1/10th the fuel, it should last 100 times longer- since the Sun lives 10 billion years an M star should live 1 trillion years.
0 out of 3 points

Incorrect, red giants are cool (to the right) and bright (toward the top)
0 out of 3 points

Question 36

Remembering that the Sun has a surface temperature of approximately 5,800 K, a main sequence A star like Vega will have a temperature of approximately:
Answer Selected Answer:

5,800 K
Correct Answer:

10,000K
Response Feedback:

Incorrect, an A star is slightly hotter than the Sun, a star at ~50,000K is an O star (the hottest stars) and all of the other choices are as cool or cooler than the Sun so would not fit an A star.
0 out of 3 points

Question 37

Imagine a star which has the same luminosity as the Sun but which has a surface temperature that is twice that of the Sun. You would then expect that a planet identical to Earth orbiting at 1 AU from this star would:
Answer Selected Answer:

be ~4x hotter than the Earth
Correct Answer:

be approximately the same temperature as the Earth
Question 38
0 out of 3 points

Pluto is now classified as a dwarf planet because:
Answer Selected Answer:

its moon Charon is too massive, so the center of mass of the system is outside Pluto it is in the Kuiper belt Incorrect, Pluto has not "cleared" its orbit. Note that it croses Neptune's orbit not that of Uranus.
0 out of 3 points

Correct Answer: Response Feedback:

Question 39

We can determine the age of a globular cluster by:
Answer Selected Answer:

counting the number of neutron stars in the cluster.
Correct Answer:

finding the spectral types of the most luminous main sequence stars.
Response Feedback:

Incorrect, the most massive/luminous main sequence stars left are the ones whose lifetime is less than the age of the cluster, so the cluster must be just older than that age. All of the stars with lifetimes less than the age of the cluster will have evolved off the main sequence already.